1. Field of the Invention
This invention relates generally to the manufacture of tubes or tubular bodies by means of hydrostatic extrusion, and more particularly to a method and apparatus for use in manufacturing tubes or tubular bodies with inner fins or with inner walls having cross-sections of irregular shapes.
2. Description of the Prior Art
Many methods are known for manufacturing tubes or tubular bodies having fins on the inner or outer peripheral surfaces thereof being designed for use, for example, in a heat exchanger or a cooling system. However, it is also known that such methods inevitably include complicated steps, such as, for instance, in the case of manufacturing tubes having inner fins, it would be even impossible to resort to a ram type extrusion method because of the construction of the tubes, unlike the case with the manufacture of tubes having outer fins, whose manufacturing method only necessitates the use of a modified die shape. Furthermore, as to the manufacture of tubes having inner fins, there has heretofore been disclosed only a primitive method wherein a tube portion and a fin portion are separately manufactured and thereafter the two portions are assembled integrally to form tubes having fins on their inner walls. However, in this method, many drawbacks are present, namely that such a method involves many complicated steps, and that there tends to be poor adhesion between the fin portion and the tube portion, with the result that there is poor heat transmission therethrough, such that the device fails to achieve the complete heat exchanging purpose being imposed on such inner fin type tubes.
Thus, as described above, the main reason for the adoption of such a complicated process lies in the inadaptability of a ram type extrusion method to the manufacturing of inner fin type tubes. Therefore, it is intended that a novel aspect of the manufacture of such inner fin type tubes be developed by adopting a hydrostatic extrusion method rather than the conventional complicated methods of ram type extrusion.